<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        #box{width: 300px;height: 300px;background: red;border:10px blue solid;
        padding: 30px;
        margin: 10px;
        }

        #box2{
            width: 300px;height: 300px;background: black; 
        }

        input{
            width: 100%;
            padding: 50px;
            box-sizing: border-box;
        }
    </style>
</head>
<body>
    <div id="box">这是一个盒子</div>
    <div id="box2">这又是一个盒子</div>
    <input type="text">
</body>
</html>